Signal apparatus for telephone-switchboards.



No. 759,771.. PATENTED MAY 10, 1904.

DE WITT U. TANNER. SIGNAL APPARATUS FOR TELEPHONE SWITGHBOARDS.

APPLICATION FILED MAR. 27, 1902.

H0 MODEL.

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fkzwjzw 176 j 7 rZMMVmM/k UNITED STATES DE WVITT C. TANNER, OF CHICAGO,

Patented May 10, 1904.

PATENT OFFICE.

ILLINOIS, ASSlC-NOR TO 'WES ERN ILLINOIS.

SIGNAL APPARATUS 0R TELEPHONE-SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent N0. '7 59,77 1, dated May10, 1904.

Application filed March 27, 1902.

T0 aZZ whom, it may concern.-

Be it known that I, I) E Wirr C. TANNEI-i, a citizen of the UnitedStates, residing at Chicago, in the county of Cook and State ofIllinois, have invented a certain new and useful Improvement in SignalApparatus for '.l.ele phone-Switchboards, of which the following is afull, clear, concise, and exact description.

My invention relates to telephone-exchange systems; and its object is toprovide improved apparatus by which the call of a subscriber for aconnection and a subsequent clearingout signal from both the subscriberswho have been connected may be automatically indicated to thecentral-oflice operator.

In accordance with my invention the linesignal, which is automaticallydisplayed to call the central ofiice, is efl aeed when the operatoranswers the call, serving thereafter as a clearing-out signal, thedisplay of which will indicate that the connection may be taken down. Incompleting connection to the called line the signal is brought under thecontrol o'l. both lines jointly, so that the apparatus of both mustcooperate to cause the display of the signal. In making connection withany line in response to a call from another the line-signal ot' thecalled. line may be blocked to avoid confusion, the signal of thecallingline only being operative. The calling plug or switch, whichcompletes connection to the called line, may be arranged to close ashunt of the line-signal of that line to render the same inoperative;and a further feature of my invention consists in the combination, withsuch an arrangement, of a battery in the shunt of insufiicient strengthto actuate the signal, but suflicient to establish a recognizable testpotential as soon as the connection is made and independent of theline-battery, which can be applied to the test-contacts only by the linerelay switch and. which consequently is applied only while the telephoneis in use at the substation.

I will describe my invention more particularly by reference to theaccompanying drawing, which is a diagram illustrating two subscriberstelephone-lines extending from sub- Serial No. 100,208. (No model.)

stations to a central-ol'fice switchboard, with a pair of plugs andtheir plug-circuit for uniting the lines, the system being organized andequipped inaccordance with my invention.

Each telephone-line extends in two limbs 1 2 from the substationapparatus to the usual multiple spring-jacks at the central oflice andthence through the high-impcdance windings a a, respectively, of theline-relay a to the poles of the battery I). At the substation the usualtelephone apparatus is provided in a bridge of the line controlled bythe usual gravity telephone-switch, said bridge being closed by theswitch when the telephone-receiver is removed from the hook for use. Thespring-jacks c are of the usual type, each having short and longline-swings 0 0 connected, respectively, with the limbs 1 2 of thetelephone-line, and also having a third contact or test ring c, which isconnected by a conductor 3 with the front contact of the line-relay a.The armature of said line-relay is connected through a resistance n withthe free pole of the grounded central battery 7). The line- 'signal maybe an incandescent lamp of in a branch 4 to ground from the test-ring cof the answering-jack. When the line-relay is excited, therefore, alocal circuit is closed from the battery 7) through the resistance a andconductors 3 4-, including the lamp (1, to earth.

The plugs) g, by which lines are united, each have the usual tip, ring,and sleeve contacts, which are adapted to engage the short andlon'g linesprings and the testa-ing, re spectively,", 01 any spring-jack intowhich the plug maybe inserted. The plug 7" is the answering-plug and gis the ealling-plu9z The tip and ring contacts f" f of the answeringplugare united with the corresponding contacts g r of the calling-plug bythe link conductors 5 6 of the plug-circuit, which include the windingsof the usual repeating-coil. The batteryb is connected in a bridgeof theplugcircuit between the windings oi the repeatingcoil in the usualinaimer, and a supervisory relay 7:. is coimected in one of thecord-strands between the battery 7) and the calling-plug, saidsupervisory relay being thus controlled by the telephone-switch at thesubstation of the line whose jack is plugged into.

A conductor 7, having two branches, which are alternatively closed bythe supervisory relay it, terminates in the third contact f of theanswering-plug, so that when the answeringplug is inserted in thespring-jack of a calling-line said conductor 7 is brought into parallelwith the line-signal (Z of such line. One of said branches of saidconductor 7, closed by the relay Zr when excited, is of low resistance,adapted to shunt out the line-signal (Z when broughtinto paralleltherewith, and the other branch, which is normally closed in the restingcontacts of the relay it, contains a battery suitable for actuating theline-signal of the calling-line when placed in circuit therewith, saidbattery, however, being connected to oppose and neutralize the flow ofcurrent from the line-battery through the signal, so that said signalwill not be excited when both batteries areapplied thereto. The sleeveof the calling-plug may be connected, through a resistance Z: and aportion of battery Z, to

earth, the resistance in being low enough to shunt out the line-signalof the called line when brought into parallel therewith. If theline-battery has an electromotive force of twenty-four volts, as isusual, the line-lamps (Z may be twelve-volt lamps. The resistances 0 maybe one hundred and twenty ohms. The resistances 73 and Z2 may be fortyohms each. The battery Z may be so proportioned and connected throughaconductor of such resistance as to supply an electromotive force oftwelve volts to conductor 7 to light the lamp (Z when the branch 3 isopened and to oppose the battery Z and prevent the lighting of said lamp(Z when the branch 3 is closed. The portion of said battery which isconnected through the resistance Z1 with the sleeve of the callingplugmay have an electromotive force of four volts.

The operation of the system is as follows: A subscriber desiring anexchange connection removes his telephone from its hook and therebycompletes the circuit from battery Z over the line through the windingsof the line-relay a, which thereupon becomes excited and draws up itsarmature. The local circuit 3 4:, including the line-lamp (Z, is thusclosed and the lamp is lighted, indicating to the operator that aconnection is desired. The operator responds to the call by insertingher answer-.

relays have dropped back. hen relay is excited and relay Z1 inert, as isthe case until the called party responds, the battery Z is brought intoconnection with the lamp (Z and sets up an electromotive force oppositeto the electromotive force applied by the battery Z, so that the lamp isextinguished. As soon as the called party responds the armature ofmagnet h is drawn up, cutting off the battery Z, but at the same timeconnecting conductor 7 to earth through the resistance Z, which shuntsthe lamp and prevents its illumination. If while the magnet Zb isexcited the relay (1. allows its armature to drop back, the lamp (Z issimply left included in the circuit 7 4, which has no battery connectedtherewith, so that the lamp remains dark; but when both relays allowtheir armatures to drop back the connection of battery Z with theline-lamp of the calling-line is cut oif and the battery Z appliedthereto in the local circuit 7 4, so that said lamp is lighted toindicate a clearing-out signal.

hen the calling-plug g is inserted into the springjack of any line, atest potential is applied to the test-rings of the several multiplespring-jacks from that portion of the battery Z which is connectedthrough resistance 7:; to the thirdcontact of said calling-plug, so thatan operator at any section on the multiple switchboard may make theusual busytest, touching the end of her calling-plug to the ring of theline being tested and listening in her telephone for the click which isproduced by the test potential. When the called party responds, thearmature of his linerelay will be drawn up, but his line-lamp will beshunted out by the resistance k. The portion of battery Z which isconnected to the third contact of the calling-plug while suflicient toestablish a recognizable test potential is not sufiicient to light thelinelamp of the called line when the line-battery thereof is cut ofi".The line-lamp of a line, therefore, is never lighted when connection ismade with said line in response to a call from some other line. Theline-signal of a calling-line is displayed to indicate the call; butwhen the operator answers the call the signal is efiaced and broughtunder the joint control of the telephone-switches at both the callingand the called stations, being thereafter displayed as a clearing-outsignal when both parties have hung up their telephones.

Having thus described my invention, I claim as new, and desire to secureby Letters Patent, the following:

1. The combination with two telephone-lines each extending from asubstation to a central oflice, of link conductors at the central ofiicefor unitingt he lines, a source of current connected with the lines atthe central oflice, a switch at each substation controllingthe flow ofcurrent in its line, electromagnetic mechanism normally associated withone line,

IIO

other electromagnetic mechanism connected with said link conductors andtemporarily associated with the other line, said electromagneticmechanism of each line being responsive to the flow of current therein,and a signal permanently associated with one of the lines and controlledjointly by the electromagnetic mechanism of both lines.

2. The combination with two telephone-lines and link conductors at thecentral o'fiice for uniting them, of magnets one for each line onemagnet being permanently connected with one line, and the other magnetbeing associated with the link conductors and temporarily rcsponsive tocurrent in the other line, said magnets being controlled respectivelythrough the agency of switches at the substations of said lines, asignal permanentlyassociated with one line and normally controlled bythe magnet thereof, and means made operative in uniting the lines forbringing said signal under the cooperative control of the magnets ofboth lines.

3. The combination with a calling-line and a called line of a line-relayfor the calling-line and a supervisory relay for the called line, saidrelays being controlled by switches at the respective substations, aline-signal for the calling-line controlled by the line-relay thereof,link conductors for uniting the lines, and circuits established inuniting the lines for connecting the line-signal of thecalling-line withcontacts of the supervisory relay of the called line, to bring saidsignal under the cooperative control of both of said relays, whereby theline-signal 01' a line may first indicate a call and thereafter serve asa disconnect-signal controlled jointly by both lines.

4. The combination with a local circuit containing a battery, aresistance and a signal, of a switch controlling said circuit, aconductor having two branches with a switch for alternatively closingeither branch, one of said branches containing a second battery, and theother branch being of low resistance, and a switch for connecting saidconductor in parallel with the signal, said last-mentioned battery beingconnected and adapted to oppose the [low of current from the firstbattery through the signal to prevent the actuation of said signal whenboth batteries are applied thereto,

said second battery being adapted to actuate the signal when connectedtherewith independent of the first battery.

5. The combination with a calling-line and a called line and theline-relays thereof controlled by switches at the respectivesubstations, of a signal for the calling-line in a local circuitcontrolled by the line-relay thereof, said circuit containing a batteryand a resist ance, link conductors for uniting the lines, a supervisoryrelay adapted to be connected through said link conductors with thecalled line and controlled through the agency of the switch at thecalled station, and a conductor? brought into parallel with theline-signal of the calling-line in making connection therewith, saidconductor having two branches controlled by said supervisory relay, oneof said branches, closed by the supervisory relay when excited, beingadapted to shunt out the linesignal, and the other branch, closed bysaid supervisory relay when inert, containing a battery, saidlast-mentioned battery being c011- nected and adapted to neutralize theline-battery, but being adapted to actuate the signal when theline-battery is disconnected.

6. The combinationwith a telephone-line having multiple spring-jackswith test-contacts, of a line-signal in a branch from the test-contactsof the spring-jacks, a source of current in a second branch from saidtest-con tacts, forming a local circuit with the firstmentioned branchcontaining said line-signal, switch-contacts of a line-relay controllingthe branch containing the source of current, a plug and plug-circuit formaking connection with the line at one of the spring-jacks thereof, ashunt of the line-signal closed in registering contacts of the plug andspring-jack, and a source of current in said shunt, serving to establisha test potential at the spring-jacks while the first-mentioned source ofcurrent is cut off, but being insufficient to actuate the line-signal.

In witness whereof I hereunto subscribe my name this 15th day ofJanuary, A. D. 1902.

DE WVITT (J. TANNER.

Witnesses:

Giuonen P. BAlrroN, E. H. ELLE'LT, Jr.

